Combined Co 2 / Tpo Measurement - Pentair HAFFMANS c-DGM Instruction Manual

6.2.5 *Combined CO
With this measurement option the CO
combined CO / O measurement. However, the total oxygen content of a package is calculated
2 2
based on the dissolved O
when a c-DGM is used in combination with an ISD sampling device.
The traditional Uhlig's method, whereby the DO value is multiplied by a Z factor (see
Appendix I) is used to calculate the TPO value.
6.2.5.1 *Sample preparation
The use of Uhlig's method is based on an oxygen balance between the oxygen dissolved in the
liquid and the oxygen in the headspace volume. The closed product package must be shaken
for five minutes to achieve this balance. After the package has been shaken, it must settle for
five minutes.
Uhlig's method also uses the proportion of the headspace volume to the liquid volume. It is
therefore important that the correct headspace volume and package volume values are stored
in the c-DGM, so that the TPO value can be calculated. These volumes can be set per product
(section 5.5.6.).
The headspace volume can be set once for a product type or individually for every sample.
There are a number of methods to measure the headspace volume and the package volume:
Volumetric measurement
If this method is used, the sample is lost. It can therefore not be used if the volume of each
separate sample has to be measured.
1. Take an accurate burette and fill it with water.
2. Ensure that the liquid level in the burette is at 0.
3. Open the product package and place it under the burette.
4. Use the burette to fill the package to the rim.
5. Read the volume used on the burette; this is the headspace volume.
6. Shake the package to empty it.
7. Refill the burette so that the liquid level is at 0.
8. Place the package back under the burette and fill it with water.
9. Read the volume used on the burette; this is the package volume.
10. A smaller burette with a smaller volume than the packaging can be used. However, this
will then need to be filled a few times and set to 0.
Weighing out the volume
If this method is used, the sample is lost. It can therefore not be used if the volume of each
separate sample has to be measured.
1. Open the product package and subsequently place it on an analytical balance.
2. Set the balance to 0.
3. Fill the package to the rim with water.
4. Read the mass on the balance, the mass in mg ≈ the headspace volume in ml.
5. Shake the package to empty it.
6. Place the package back on the balance and set it back to 0.
7. Fill the package to the rim with water.
8. Read the mass on the balance, the mass in mg ≈ the package volume in ml.
c-DGM/i-DGM
/ TPO measurement
2
and O
2
value measured. This measuring method can therefore only be used
2
, &&D E^ 'D 'D
proceeds in the same manner as in the
2
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